The invention relates to a ventilation system, in particular for use in the agricultural field, comprising at least one ventilator which is coupled to an electromotor comprising at least one excitation winding, which is connected to a voltage source via a control unit, whereby said control unit includes a processor module comprising a digital computing circuit and at least one memory for storing control software and control quantities, which processor module includes communication means for exchanging data between the processor module and a remote central processing unit via a communication link.
A ventilation system of the above kind is disclosed in published European Patent Application No. 0 545 499. In this known system a ventilator is controlled by means of a remote central processing unit, which transmits control signals via a communication link to a processor module incorporated in the ventilator, which controls the ventilator on the basis of the signals being received. The processor module furthermore transmits status signals, such as the rotational speed and temperature of the ventilator, to the central processing unit, which in turn utilizes these signals for controlling the ventilator. A drawback of this known system for the remote control of one or more ventilators is the fact that in case of failure of the central processing unit and/or of the communication link between said unit and the processor module, all ventilators in the system will stop, with all its consequences. The aforesaid European document furthermore makes mention of the fact that in case of failure of the central processing unit and/or of the communication link, the processor module will control the ventilator to a preset ventilation level. Although the ventilator will not stop in that case but will continue to operate at a predetermined ventilation level, it will be apparent that under certain circumstances said ventilation level may differ rather much from the ventilation level which is desired in order to maintain the conditions in the space ventilated by the ventilator at an acceptable level. Ventilators of the kind to which the invention relates are frequently used in the agricultural field for ventilating cattle and poultry houses, for example, whereby the conditions in these spaces must be critically maintained at a precisely determined level. If the ventilator falls back to a predetermined fixed ventilation level in case of failure of the central processing unit and/or of the communication link, as is the case with the known system, the conditions in the space to be ventilated may become unacceptable after a very short time already.